its not updating, its adding another firefox. Your current version of firefox stays how it is, so you can have FireFox 3.6 open and FireFox 4 beta open at the same time.
It's worth trying it out. And besides, if you give your feedback on what you like and dislike and enough people agree, they could take that out or keep that in.
As soon as I downloaded FF4, I fell in love with it again, after being a great fan of Chrome I'm back with firefox again. I think at the moment firefox 4 is faster than Google Chrome 😀
Is it like always in "full screen mode", More in the sense it has Firefox address bar and all that, But when you go to the bottom to open win 7's task bar it won't open cause it's in "full screen", Does that happen to you?